Field of the Invention
The present invention relates to a lithography apparatus, a lithography method, and an article manufacturing method.
Description of the Related Art
In a lithography process included in a manufacturing process of articles such as semiconductor devices or liquid crystal display devices, a lithography apparatus forms a machining pattern on a work piece (e.g., a substrate). The pertinent pattern may include a latent image pattern in a resist, or a pattern of a resist itself. An exposure apparatus, which is an example of this lithography apparatus, projects a pattern that is pre-formed on an original (a reticle, mask, or the like) via a projection optical system, and exposes a substrate (a wafer, glass plate, or the like) to which a photosensitizer has been applied. With this exposure apparatus, prior to exposure, positioning (alignment) is conducted to overlay the pattern formed in the original onto a pattern formed on a substrate.
For the pertinent alignment, the AGA (advanced global alignment) method is known as a technique for obtaining positions of each of various shot regions on a substrate. With the AGA method, first, several sample shot regions are selected from among all shot regions on a substrate, and a positional displacement amount of each sample shot region from its design position (reference position, or position in terms of design) is measured. Based on the obtained measurement results, correction parameters (hereinafter “substrate correction parameters”) are then obtained in order to obtain the positions of the respective shot regions from their design positions (correct the design positions). The pertinent substrate correction parameter may serve as a coefficient of a formula (regression formula) for conversion from a previously prepared design position of a given shot region to a (actual or measured) position of a given shot region. The pertinent coefficient may be obtained by regression computation based on the pertinent conversion formula and the aforementioned measurement results. To increase the precision of overlay, in addition to substrate correction parameters, there are also techniques for obtaining parameters (hereinafter “shot correction parameters”) for obtaining the forms of shot regions (correcting a design form (a reference form, or a form in terms of design) of shot regions). The form of a shot region typically pertains to magnification and rotation respectively relating to the X axis and the Y axis. The pertinent shot correction parameter may be used as a coefficient for a formula (regression formula) for converting from a previously prepared design position inside a given shot region to a (actual or measured) position inside a given shot region. The pertinent coefficient may be obtained by regression computation based on the pertinent conversion formula and the aforementioned measurement results. The causes of shot region deformation include those deriving from the exposure step such as distortion of the projection optical system, and those deriving from other steps such as substrate deformation in steps other than the exposure step involving heat.
With the AGA method, the position of a mark (alignment mark) corresponding to a shot region is measured to obtain a displacement amount of a representative position (normally the center) of a shot region from its design position. FIG. 9 consists of plan views which show mark arrangements pertaining to a conventional shot region SH. FIG. 9(a) is a drawing which exemplifies an arrangement of marks related to a shot region SH that are required to obtain a substrate correction parameter. There is arrangement of a mark MX1 for measurement of a position in the X axis direction, and a mark MY1 for measurement of a position in the Y axis direction. On the other hand, FIG. 9(b) is a drawing which exemplifies an arrangement of marks related to a shot region SH that are required to obtain a shot correction parameter. A larger number of marks (marks MX1-MX3, and marks MY1-MY3) are arranged than in FIG. 9(a). FIG. 10 is a plan view which exemplifies an arrangement of sample shot regions SH on a substrate W. Two sample shot regions SH1 and SH2 like the one shown in FIG. 9(b) are set up on the substrate W for obtaining shot correction parameters. Four sample shot regions SH3-SH6 like the one shown in FIG. 9(a) are set up on the substrate W for obtaining substrate correction parameters. Japanese Patent Application Laid-Open No. 2003-100604 discloses a method for obtaining substrate correction parameters and shot correction parameters, and an exposure apparatus employing it.
With respect to the method shown in Japanese Patent Application Laid-Open No. 2003-100604, in order to obtain shot correction parameters, dedicated sample shot regions are measured that are separate from the sample shot regions for obtaining substrate correction parameters. Consequently, a conventional exposure apparatus takes time for measurement of mark positions, and can be disadvantageous in terms of throughput.